HI @opux ,
The problem you are having is probably due to the liquid spill and the issue could be the following;
# The battery charging circuit is damaged, suspecting that the diode on the input that merges the battery and the charger line is faulty. It happens on older Macbooks, seen that before. Sometimes it can even occur without any exposure to liquid.
# Faulty battery (due to water spill or age)
The bare metal showing is not a huge issue, you only removed the contact damper plastic/silicone stickers that hide the bare magnets. You should feel that the charging connector holds stronger on the magnets now.
I would take out the whole motherboard and have a closer look to make sure that there are no other parts liquid damaged.
If I were you, I would take out the battery until you diagnosed where the fault lies, in case you (further) damage your battery as it might be saved.